Organophotoreceptor with charge transport material having bis(9-fluorenone) azine groups

ABSTRACT

Improved organophotoreceptor comprises an electrically conductive substrate and a photoconductive element on the electrically conductive substrate, the photoconductive element comprising: 
 
(a) a charge transport material having the formula  
                 
where n is an integer between 2 and 6, inclusive; 
         R 1  and R 2  are, independently, H, halogen, carboxyl, hydroxyl, thiol, cyano, nitro, aldehyde group, ketone group, an ether group, an ester group, a carbonyl group, an alkyl group, an alkaryl group, or an aryl group;    X is a linking group having the formula —(CH 2 ) m —, branched or linear, where m is an integer between 0 and 20, inclusive, and one or more of the methylene groups can be optionally replaced by O, S, C═O, O═S═O, a heterocyclic group, an aromatic group, urethane, urea, an ester group, a NR 3  group, a CHR 4  group, or a CR 5 R 6  group where R 3 , R 4 , R 5 , and R 6  are, independently, H, an alkyl group, an alkaryl group, a heterocyclic group, or an aryl group;    Y comprises a bond, C, N, O, S, a branched or linear —(CH 2 ) p — group where p is an integer between 0 and 10, an aromatic group, a cycloalkyl group, a heterocyclic group, or a NR 9  group where R 9  is hydrogen atom, an alkyl group, or aryl group, wherein Y has a structure selected to form n bonds with the corresponding X groups; and Z is a fluorenylidene group; and (b) a charge generating compound. Corresponding electrophotographic apparatuses and imaging methods are described.

FIELD OF THE INVENTION

This invention relates to organophotoreceptors suitable for use inelectrophotography and, more specifically, to organophotoreceptorshaving a charge transport material with at least two bis(9-fluorenone)azine groups.

BACKGROUND OF THE INVENTION

In electrophotography, an organophotoreceptor in the form of a plate,disk, sheet, belt, drum or the like having an electrically insulatingphotoconductive element on an electrically conductive substrate isimaged by first uniformly electrostatically charging the surface of thephotoconductive layer, and then exposing the charged surface to apattern of light. The light exposure selectively dissipates the chargein the illuminated areas where light strikes the surface, therebyforming a pattern of charged and uncharged areas, referred to as alatent image. A liquid or solid toner is then provided in the vicinityof the latent image, and toner droplets or particles deposit in thevicinity of either the charged or uncharged areas to create a tonedimage on the surface of the photoconductive layer. The resulting tonedimage can be transferred to a suitable ultimate or intermediatereceiving surface, such as paper, or the photoconductive layer canoperate as an ultimate receptor for the image. The imaging process canbe repeated many times to complete a single image, for example, byoverlaying images of distinct color components or effect shadow images,such as overlaying images of distinct colors to form a full color finalimage, and/or to reproduce additional images.

Both single layer and multilayer photoconductive elements have beenused. In single layer embodiments, a charge transport material andcharge generating material are combined with a polymeric binder and thendeposited on the electrically conductive substrate. In multilayerembodiments, the charge transport material and charge generatingmaterial are present in the element in separate layers, each of whichcan optionally be combined with a polymeric binder, deposited on theelectrically conductive substrate. Two arrangements are possible for atwo-layer photoconductive element. In one two-layer arrangement (the“dual layer” arrangement), the charge-generating layer is deposited onthe electrically conductive substrate and the charge transport layer isdeposited on top of the charge generating layer. In an alternatetwo-layer arrangement (the “inverted dual layer” arrangement), the orderof the charge transport layer and charge generating layer is reversed.

In both the single and multilayer photoconductive elements, the purposeof the charge generating material is to generate charge carriers (i.e.,holes and/or electrons) upon exposure to light. The purpose of thecharge transport material is to accept at least one type of these chargecarriers and transport them through the charge transport layer in orderto facilitate discharge of a surface charge on the photoconductiveelement. The charge transport material can be a charge transportcompound, an electron transport compound, or a combination of both. Whena charge transport compound is used, the charge transport compoundaccepts the hole carriers and transports them through the layer with thecharge transport compound. When an electron transport compound is used,the electron transport compound accepts the electron carriers andtransports them through the layer with the electron transport compound.

SUMMARY OF THE INVENTION

This invention provides organophotoreceptors having good electrostaticproperties such as high V_(acc) and low V_(dis).

In a first aspect, an organophotoreceptor comprises an electricallyconductive substrate and a photoconductive element on the electricallyconductive substrate, the photoconductive element comprising:

-   -   (a) a charge transport material having the formula    -   where n is an integer between 2 and 6, inclusive;    -   R₁ and R₂ are, independently, H, halogen, carboxyl, hydroxyl,        thiol, cyano, nitro, aldehyde group, ketone group, an ether        group, an ester group, a carbonyl group, an alkyl group, an        alkaryl group, or an aryl group;    -   X is a linking group having the formula —(CH₂)_(m)—, branched or        linear, where m is an integer between 0 and 20, inclusive, and        one or more of the methylene groups can be optionally replaced        by O, S, C═O, O═S═O, a heterocyclic group, an aromatic group,        urethane, urea, an ester group, a NR₃ group, a CHR₄ group, or a        CR₅R₆ group where R₃, R₄, R₅, and R₆ are, independently, H, an        alkyl group, an alkaryl group, a heterocyclic group, or an aryl        group;    -   Y is a bond, C, N, O, S, a branched or linear —(CH₂)_(p)— group        where p is an integer between 0 and 10 and where one or more of        the hydrogen atoms in the —(CH₂)_(p)— may be optionally removed        to provide bond positions to enable n to have a higher value        than 2, an aromatic group, a cycloalkyl group, a heterocyclic        group, or a NR₇ group where R₇ is hydrogen atom, an alkyl group,        or aryl group; and    -   Z is a fluorenylidene group; and    -   (b) a charge generating compound.

The organophotoreceptor may be provided, for example, in the form of aplate, a flexible belt, a flexible disk, a sheet, a rigid drum, or asheet around a rigid or compliant drum. In one embodiment, theorganophotoreceptor includes: (a) a photoconductive element comprisingthe charge transport material, the charge generating compound, a secondcharge transport material, and a polymeric binder; and (b) theelectrically conductive substrate.

In a second aspect, the invention features an electrophotographicimaging apparatus that comprises (a) a light imaging component; and (b)the above-described organophotoreceptor oriented to receive light fromthe light imaging component. The apparatus can further comprise a liquidtoner dispenser. The method of electrophotographic imaging, with thephotoreceptors containing the above noted charge transport materials, isalso described.

In a third aspect, the invention features an electrophotographic imagingprocess that includes (a) applying an electrical charge to a surface ofthe above-described organophotoreceptor; (b) imagewise exposing thesurface of the organophotoreceptor to radiation to dissipate charge inselected areas and thereby form a pattern of at least relatively chargedand uncharged areas on the surface; (c) contacting the surface with atoner, such as a liquid toner that includes a dispersion of colorantparticles in an organic liquid, to create a toned image; and (d)transferring the toned image to a substrate.

In a fourth aspect, the invention features a charge transport materialhaving the general Formula (1) above.

The invention provides suitable charge transport materials fororganophotoreceptors featuring a combination of good mechanical andelectrostatic properties. These photoreceptors can be used successfullywith liquid toners to produce high quality images. The high quality ofthe imaging system can be maintained after repeated cycling.

Other features and advantages of the invention will be apparent from thefollowing description of the particular embodiments thereof, and fromthe claims.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

An organophotoreceptor as described herein has an electricallyconductive substrate and a photoconductive element comprising a chargegenerating compound and a charge transport material having two or morebis(9-fluorenone) azine groups linked through a linking group. Thesecharge transport materials have desirable properties as evidenced bytheir performance in organophotoreceptors for electrophotography. Inparticular, the charge transport materials of this invention have highcharge carrier mobilities and good compatibility with various bindermaterials, and possess excellent electrophotographic properties. Theorganophotoreceptors according to this invention generally have a highphotosensitivity, a low residual potential, and a high stability withrespect to cycle testing, crystallization, and organophotoreceptorbending and stretching. The organophotoreceptors are particularly usefulin laser printers and the like as well as fax machines, photocopiers,scanners and other electronic devices based on electrophotography. Theuse of these charge transport materials is described in more detailbelow in the context of laser printer use, although their application inother devices operating by electrophotography can be generalized fromthe discussion below.

To produce high quality images, particularly after multiple cycles, itis desirable for the charge transport materials to form a homogeneoussolution with the polymeric binder and remain approximatelyhomogeneously distributed through the organophotoreceptor materialduring the cycling of the material. In addition, it is desirable toincrease the amount of charge that the charge transport material canaccept (indicated by a parameter known as the acceptance voltage or“V_(acc)”), and to reduce retention of that charge upon discharge(indicated by a parameter known as the discharge voltage or “V_(dis)”).

The charge transport materials can be classified as a charge transportcompound or an electron transport compound. There are many chargetransport compounds and electron transport compounds known in the artfor electrophotography. Non-limiting examples of charge transportcompounds include, for example, pyrazoline derivatives, fluorenederivatives, oxadiazole derivatives, stilbene derivatives, hydrazonederivatives, carbazole hydrazone derivatives, triaryl amines, polyvinylcarbazole, polyvinyl pyrene, polyacenaphthylene, or multi-hydrazonecompounds comprising at least two hydrazone groups and at least twogroups selected from the group consisting ofp-(N,N-disubstituted)arylamine such as triphenylamine and heterocyclessuch as carbazole, julolidine, phenothiazine, phenazine, phenoxazine,phenoxathiin, thiazole, oxazole, isoxazole, dibenzo(1,4)dioxine,thianthrene, imidazole, benzothiazole, benzotriazole, benzoxazole,benzimidazole, quinoline, isoquinoline, quinoxaline, indole, indazole,pyrrole, purine, pyridine, pyridazine, pyrimidine, pyrazine, triazole,oxadiazole, tetrazole, thiadiazole, benzisoxazole, benzisothiazole,dibenzofuran, dibenzothiophene, thiophene, thianaphthene, quinazoline,or cinnoline.

Non-limiting examples of electron transport compounds include, forexample, bromoaniline, tetracyanoethylene, tetracyanoquinodimethane,2,4,7-trinitro-9-fluorenone, 2,4,5,7-tetranitro-9-fluorenone,2,4,5,7-tetranitroxanthone, 2,4,8-trinitrothioxanthone,2,6,8-trinitro-indeno4H-indeno[1,2-b]thiophene-4-one, and1,3,7-trinitrodibenzo thiophene-5,5-dioxide,(2,3-diphenyl-1-indenylidene)malononitrile, 4H-thiopyran-1,1-dioxide andits derivatives such as4-dicyanomethylene-2,6-diphenyl-4H-thiopyran-1,1-dioxide,4-dicyanomethylene-2,6-di-m-tolyl-4H-thiopyran-1,1-dioxide, andunsymmetrically substituted 2,6-diaryl-4H-thiopyran-1,1-dioxide such as4H-1,1-dioxo-2-(p-isopropylphenyl)-6-phenyl-4-(dicyanomethylidene)thiopyranand4H-1,1-dioxo-2-(p-isopropylphenyl)-6-(2-thienyl)-4-(dicyanomethylidene)thiopyran,derivatives of phospha-2,5-cyclohexadiene,alkoxycarbonyl-9-fluorenylidene)malononitrile derivatives such as(4-n-butoxycarbonyl-9-fluorenylidene)malononitrile,(4-phenethoxycarbonyl-9-fluorenylidene)malononitrile,(4-carbitoxy-9-fluorenylidene)malononitrile, anddiethyl(4-n-butoxycarbonyl-2,7-dinitro-9-fluorenylidene)-malonate,anthraquinodimethane derivatives such as11,11,12,12-tetracyano-2-alkylanthraquinodimethane and11,11-dicyano-12,12-bis(ethoxycarbonyl)anthraquinodimethane, anthronederivatives such as 1-chloro-10-[bis(ethoxycarbonyl)methylene]anthrone,1,8-dichloro-10-[bis(ethoxycarbonyl)methylene]anthrone,1,8-dihydroxy-10-[bis(ethoxycarbonyl)methylene]anthrone, and1-cyano-10-[bis(ethoxycarbonyl)methylene)anthrone,7-nitro-2-aza-9-fluroenylidene-malononitrile, diphenoquinonederivatives, benzoquinone derivatives, naphtoquinone derivatives,quinine derivatives, tetracyanoethylenecyanoethylene, 2,4,8-trinitrothioxantone, dinitrobenzene derivatives, dinitroanthracene derivatives,dinitroacridine derivatives, nitroanthraquinone derivatives,dinitroanthraquinone derivatives, succinic anhydride, maleic anhydride,dibromo maleic anhydride, pyrene derivatives, carbazole derivatives,hydrazone derivatives, N,N-dialkylaniline derivatives, diphenylaminederivatives, triphenylamine derivatives, triphenylmethane derivatives,tetracyano quinoedimethane, 2,4,5,7-tetranitro-9-fluorenone,2,4,7-trinitro-9-dicyanomethylene fluorenone, 2,4,5,7-tetranitroxanthonederivatives, and 2,4,8-trinitrothioxanthone derivatives. In someembodiments of interest, the electron transport compound comprises an(alkoxycarbonyl-9-fluorenylidene)malononitrile derivative, such as(4-n-butoxycarbonyl-9-fluorenylidene)malononitrile.

Although there are many charge transport materials available, there is aneed for other charge transport materials to meet the variousrequirements of particular electrophotography applications.

In electrophotography applications, a charge-generating compound withinan organophotoreceptor absorbs light to form electron-hole pairs. Theseelectrons and holes can be transported over an appropriate time frameunder a large electric field to discharge locally a surface charge thatis generating the field. The discharge of the field at a particularlocation results in a surface charge pattern that essentially matchesthe pattern drawn with the light. This charge pattern then can be usedto guide toner deposition. The charge transport materials describedherein are especially effective at transporting charge, and inparticular electrons from the electron-hole pairs formed by the chargegenerating compound. In some embodiments, a specific electron transportcompound or charge transport compound can also be used along with thecharge transport material of this invention.

The layer or layers of materials containing the charge generatingcompound and the charge transport materials are within anorganophotoreceptor. To print a two dimensional image using theorganophotoreceptor, the organophotoreceptor has a two dimensionalsurface for forming at least a portion of the image. The imaging processthen continues by cycling the organophotoreceptor to complete theformation of the entire image and/or for the processing of subsequentimages.

The organophotoreceptor may be provided in the form of a plate, aflexible belt, a disk, a rigid drum, a sheet around a rigid or compliantdrum, or the like. The charge transport material can be in the samelayer as the charge generating compound and/or in a different layer fromthe charge generating compound. Additional layers can be used also, asdescribed further below.

In some embodiments, the organophotoreceptor material comprises, forexample: (a) a charge transport layer comprising the charge transportmaterial and a polymeric binder; (b) a charge generating layercomprising the charge generating compound and a polymeric binder; and(c) the electrically conductive substrate. The charge transport layermay be intermediate between the charge generating layer and theelectrically conductive substrate. Alternatively, the charge generatinglayer may be intermediate between the charge transport layer and theelectrically conductive substrate. In further embodiments, theorganophotoreceptor material has a single layer with both a chargetransport material and a charge generating compound within a polymericbinder.

The organophotoreceptors can be incorporated into an electrophotographicimaging apparatus, such as laser printers. In these devices, an image isformed from physical embodiments and converted to a light image that isscanned onto the organophotoreceptor to form a surface latent image. Thesurface latent image can be used to attract toner onto the surface ofthe organophotoreceptor, in which the toner image is the same or thenegative of the light image projected onto the organophotoreceptor. Thetoner can be a liquid toner or a dry toner. The toner is subsequentlytransferred, from the surface of the organophotoreceptor, to a receivingsurface, such as a sheet of paper. After the transfer of the toner, theentire surface is discharged, and the material is ready to cycle again.The imaging apparatus can further comprise, for example, a plurality ofsupport rollers for transporting a paper receiving medium and/or formovement of the photoreceptor, a light imaging component with suitableoptics to form the light image, a light source, such as a laser, a tonersource and delivery system and an appropriate control system.

An electrophotographic imaging process generally can comprise (a)applying an electrical charge to a surface of the above-describedorganophotoreceptor; (b) imagewise exposing the surface of theorganophotoreceptor to radiation to dissipate charge in selected areasand thereby form a pattern of charged and uncharged areas on thesurface; (c) exposing the surface with a toner, such as a liquid tonerthat includes a dispersion of colorant particles in an organic liquid tocreate a toner image, to attract toner to the charged or dischargedregions of the organophotoreceptor; and (d) transferring the toner imageto a substrate.

As described herein, an organophotoreceptor comprises a charge transportmaterial having the formula

where n is an integer between 2 and 6, inclusive;

-   -   R₁ and R₂ are, independently, H, halogen, carboxyl, hydroxyl,        thiol, cyano, nitro, aldehyde group, ketone group, an ether        group, an ester group, a carbonyl group, an alkyl group, an        alkaryl group, or an aryl group;    -   X is a linking group having the formula —(CH₂)_(m)—, branched or        linear, where m is an integer between 0 and 20, inclusive, and        one or more of the methylene groups can be optionally replaced        by O, S, C═O, O═S═O, a heterocyclic group, an aromatic group,        urethane, urea, an ester group, a NR₃ group, a CHR₄ group, or a        CR₅R₆ group where R₃, R₄, R₅, and R₆ are, independently, H, an        alkyl group, an alkaryl group, a heterocyclic group, or an aryl        group;    -   Y is a bond, C, N, O, S, a branched or linear —(CH₂)_(p)— group        where p is an integer between 0 and 10 and where one or more of        the hydrogen atoms in the —(CH₂)_(p)— may be optionally removed        to provide bond positions to enable n to have a higher value        than 2, an aromatic group, a cycloalkyl group, a heterocyclic        group, or a NR₇ group where R₇ is hydrogen atom, an alkyl group,        or aryl group; and    -   Z is a fluorenylidene group.

Substitution is liberally allowed on the chemical groups to affectvarious physical effects on the properties of the compounds, such asmobility, sensitivity, solubility, stability, and the like, as is knowngenerally in the art. In the description of chemical substituents, thereare certain practices common to the art that are reflected in the use oflanguage. The term group indicates that the generically recited chemicalentity (e.g., alkyl group, phenyl group, aromatic group, etc.) may haveany substituent thereon, which is consistent with the bond structure ofthat group. For example, where the term ‘alkyl group’ is used, that termwould not only include unsubstituted liner, branched and cyclic alkyls,such as methyl, ethyl, isopropyl, tert-butyl, cyclohexyl, dodecyl andthe like, but also substituents such as hydroxyethyl, cyanobutyl,1,2,3-trichloropropane, and the like. However, as is consistent withsuch nomenclature, no substitution would be included within the termthat would alter the fundamental bond structure of the underlying group.For example, where a phenyl group is recited, substitution such as1-hydroxyphenyl, 2,4-fluorophenyl, orthocyanophenyl,1,3,5-trimethoxyphenyl and the like would be acceptable within theterminology, while substitution of 1,1,2,2,3,3-hexamethylphenyl wouldnot be acceptable as that substitution would require the ring bondstructure of the phenyl group to be altered to a non-aromatic formbecause of the substitution. Aromatic group is a group comprises a 4n+2pi electron system where n is any integer. When referring to an aromaticgroup, the substituent cited will include any substitution that does notsubstantively alter the chemical nature of the 4n+2 pi electron systemin the aromatic group. Where the term moiety is used, such as alkylmoiety or phenyl moiety, that terminology indicates that the chemicalmaterial is not substituted. Where the term alkyl moiety is used, thatterm represents only an unsubstituted alkyl hydrocarbon group, whetherbranched, straight chain, or cyclic.

Organophotoreceptors

The organophotoreceptor may be, for example, in the form of a plate, asheet, a flexible belt, a disk, a rigid drum, or a sheet around a rigidor compliant drum, with flexible belts and rigid drums generally beingused in commercial embodiments. The organophotoreceptor may comprise,for example, an electrically conductive substrate and on theelectrically conductive substrate a photoconductive element in the formof one or more layers. The photoconductive element can comprise both acharge transport material and a charge generating compound in apolymeric binder, which may or may not be in the same layer, as well asa second charge transport material such as a charge transport compoundor an electron transport compound in some embodiments. For example, thecharge transport material and the charge generating compound can be in asingle layer. In other embodiments, however, the photoconductive elementcomprises a bilayer construction featuring a charge generating layer anda separate charge transport layer. The charge generating layer may belocated intermediate between the electrically conductive substrate andthe charge transport layer. Alternatively, the photoconductive elementmay have a structure in which the charge transport layer is intermediatebetween the electrically conductive substrate and the charge generatinglayer.

The electrically conductive substrate may be flexible, for example inthe form of a flexible web or a belt, or inflexible, for example in theform of a drum. A drum can have a hollow cylindrical structure thatprovides for attachment of the drum to a drive that rotates the drumduring the imaging process. Typically, a flexible electricallyconductive substrate comprises an electrically insulating substrate anda thin layer of electrically conductive material onto which thephotoconductive material is applied.

The electrically insulating substrate may be paper or a film formingpolymer such as polyester (e.g., polyethylene terephthalate orpolyethylene naphthalate), polyimide, polysulfone, polypropylene, nylon,polyester, polycarbonate, polyvinyl resin, polyvinyl fluoride,polystyrene and the like. Specific examples of polymers for supportingsubstrates included, for example, polyethersulfone (Stabar™ S-100,available from ICI), polyvinyl fluoride (Tedlar®, available from E.I.DuPont de Nemours & Company), polybisphenol-A polycarbonate (Makrofol™,available from Mobay Chemical Company) and amorphous polyethyleneterephthalate (Melinar™, available from ICI Americas, Inc.). Theelectrically conductive materials may be graphite, dispersed carbonblack, iodide, conductive polymers such as polypyroles and Calgon®conductive polymer 261 (commercially available from Calgon Corporation,Inc., Pittsburgh, Pa.), metals such as aluminum, titanium, chromium,brass, gold, copper, palladium, nickel, or stainless steel, or metaloxide such as tin oxide or indium oxide. In embodiments of particularinterest, the electrically conductive material is aluminum. Generally,the photoconductor substrate has a thickness adequate to provide therequired mechanical stability. For example, flexible web substratesgenerally have a thickness from about 0.01 to about 1 mm, while drumsubstrates generally have a thickness of from about 0.5 mm to about 2mm.

The charge generating compound is a material that is capable ofabsorbing light to generate charge carriers, such as a dye or pigment.Non-limiting examples of suitable charge generating compounds include,for example, metal-free phthalocyanines (e.g., ELA 8034 metal-freephthalocyanine available from H.W. Sands, Inc. or Sanyo Color Works,Ltd., CGM-X01), metal phthalocyanines such as titanium phthalocyanine,copper phthalocyanine, oxytitanium phthalocyanine (also referred to astitanyl oxyphthalocyanine, and including any crystalline phase ormixtures of crystalline phases that can act as a charge generatingcompound), hydroxygallium phthalocyanine, squarylium dyes and pigments,hydroxy-substituted squarylium pigments, perylimides, polynuclearquinones available from Allied Chemical Corporation under the tradenameIndofast® Double Scarlet, Indofast® Violet Lake B, Indofast® BrilliantScarlet and Indofast® Orange, quinacridones available from DuPont underthe tradename Monastral™ Red, Monastral™ Violet and Monastral™ Red Y,naphthalene 1,4,5,8-tetracarboxylic acid derived pigments including theperinones, tetrabenzoporphyrins and tetranaphthaloporphyrins, indigo-and thioindigo dyes, benzothioxanthene-derivatives, perylene3,4,9,10-tetracarboxylic acid derived pigments, polyazo-pigmentsincluding bisazo-, trisazo- and tetrakisazo-pigments, polymethine dyes,dyes containing quinazoline groups, tertiary amines, amorphous selenium,selenium alloys such as selenium-tellurium, selenium-tellurium-arsenicand selenium-arsenic, cadmium sulphoselenide, cadmium selenide, cadmiumsulphide, and mixtures thereof. For some embodiments, the chargegenerating compound comprises oxytitanium phthalocyanine (e.g., anyphase thereof), hydroxygallium phthalocyanine or a combination thereof.

The photoconductive layer of this invention may optionally contain asecond charge transport material which may be a charge transportcompound, an electron transport compound, or a combination of both.Generally, any charge transport compound or electron transport compoundknown in the art can be used as the second charge transport material.

An electron transport compound and a UV light stabilizer can have asynergistic relationship for providing desired electron flow within thephotoconductor. The presence of the UV light stabilizers alters theelectron transport properties of the electron transport compounds toimprove the electron transporting properties of the composite. UV lightstabilizers can be ultraviolet light absorbers or ultraviolet lightinhibitors that trap free radicals.

UV light absorbers can absorb ultraviolet radiation and dissipate it asheat. UV light inhibitors are thought to trap free radicals generated bythe ultraviolet light and after trapping of the free radicals,subsequently to regenerate active stabilizer moieties with energydissipation. In view of the synergistic relationship of the UVstabilizers with electron transport compounds, the particular advantagesof the UV stabilizers may not be their UV stabilizing abilities,although the UV stabilizing ability may be further advantageous inreducing degradation of the organophotoreceptor over time. The improvedsynergistic performance of organophotoreceptors with layers comprisingboth an electron transport compound and a UV stabilizer are describedfurther in copending U.S. patent application Ser. No. 10/425,333 filedon Apr. 28, 2003 to Zhu, entitled “Organophotoreceptor With A LightStabilizer,” incorporated herein by reference.

Non-limiting examples of suitable light stabilizer include, for example,hindered trialkylamines such as Tinuvin 144 and Tinuvin 292 (from CibaSpecialty Chemicals, Terrytown, N.Y.), hindered alkoxydialkylamines suchas Tinuvin 123 (from Ciba Specialty Chemicals), benzotriazoles such asTinuvan 328, Tinuvin 900 and Tinuvin 928 (from Ciba SpecialtyChemicals), benzophenones such as Sanduvor 3041 (from Clariant Corp.,Charlotte, N.C.), nickel compounds such as Arbestab (from RobinsonBrothers Ltd, West Midlands, Great Britain), salicylates,cyanocinnamates, benzylidene malonates, benzoates, oxanilides such asSanduvor VSU (from Clariant Corp., Charlotte, N.C.), triazines such asCyagard UV-1164 (from Cytec Industries Inc., N.J.), polymeric stericallyhindered amines such as Luchem (from Atochem North America, Buffalo,N.Y.). In some embodiments, the light stabilizer is selected from thegroup consisting of hindered trialkylamines having the followingformula:

where R₁, R₂, R₃, R₄, R₆, R₇, R₈, R₁₀, R₁₁, R₁₂, R₁₃, R₁₄, R₁₅ are,independently, hydrogen, alkyl group, or ester, or ether group; and R₅,R₉, and R₁₄ are, independently, alkyl group; and X is a linking groupselected from the group consisting of —O—CO—(CH₂)_(m)—CO—O— where m isbetween 2 to 20.

The binder generally is capable of dispersing or dissolving the chargetransport material (in the case of the charge transport layer or asingle layer construction), the charge generating compound (in the caseof the charge generating layer or a single layer construction) and/or anelectron transport compound for appropriate embodiments. Examples ofsuitable binders for both the charge generating layer and chargetransport layer generally include, for example,polystyrene-co-butadiene, polystyrene-co-acrylonitrile, modified acrylicpolymers, polyvinyl acetate, styrene-alkyd resins, soya-alkyl resins,polyvinylchloride, polyvinylidene chloride, polyacrylonitrile,polycarbonates, polyacrylic acid, polyacrylates, polymethacrylates,styrene polymers, polyvinyl butyral, alkyd resins, polyamides,polyurethanes, polyesters, polysulfones, polyethers, polyketones,phenoxy resins, epoxy resins, silicone resins, polysiloxanes,poly(hydroxyether) resins, polyhydroxystyrene resins, novolak,poly(phenylglycidyl ether)-co-dicyclopentadiene, copolymers of monomersused in the above-mentioned polymers, and combinations thereof. Suitablebinders include, for example, polyvinyl butyral, such as BX-1 and BX-5from Sekisui Chemical Co. Ltd., Japan.

Suitable optional additives for any one or more of the layers include,for example, antioxidants, coupling agents, dispersing agents, curingagents, surfactants, and combinations thereof.

The photoconductive element overall typically has a thickness from about10 to about 45 microns. In the dual layer embodiments having a separatecharge generating layer and a separate charge transport layer, thecharge generation layer generally has a thickness form about 0.5 toabout 2 microns, and the charge transport layer has a thickness fromabout 5 to about 35 microns. In embodiments in which the chargetransport material and the charge generating compound are in the samelayer, the layer with the charge generating compound and the chargetransport composition generally has a thickness from about 7 to about 30microns. In embodiments with a distinct electron transport layer, theelectron transport layer has an average thickness from about 0.5 micronsto about 10 microns and in further embodiments from about 1 micron toabout 3 microns. In general, an electron transport overcoat layer canincrease mechanical abrasion resistance, increases resistance to carrierliquid and atmospheric moisture, and decreases degradation of thephotoreceptor by corona gases. A person of ordinary skill in the artwill recognize that additional ranges of thickness within the explicitranges above are contemplated and are within the present disclosure.

Generally, for the organophotoreceptors described herein, the chargegeneration compound is in an amount from about 0.5 to about 25 weightpercent in further embodiments in an amount from about 1 to about 15weight percent and in other embodiments in an amount from about 2 toabout 10 weight percent, based on the weight of the photoconductivelayer. The charge transport material is in an amount from about 10 toabout 80 weight percent, based on the weight of the photoconductivelayer, in further embodiments in an amount from about 35 to about 60weight percent, and in other embodiments from about 45 to about 55weight percent, based on the weight of the photoconductive layer. Theoptional second charge transport material, when present, can be in anamount of at least about 2 weight percent, in other embodiments fromabout 2.5 to about 25 weight percent, based on the weight of thephotoconductive layer, and in further embodiments in an amount fromabout 4 to about 20 weight percent, based on the weight of thephotoconductive layer. The binder is in an amount from about 15 to about80 weight percent, based on the weight of the photoconductive layer, andin further embodiments in an amount from about 20 to about 75 weightpercent, based on the weight of the photoconductive layer. A person ofordinary skill in the art will recognize that additional ranges withinthe explicit ranges of compositions are contemplated and are within thepresent disclosure.

For the dual layer embodiments with a separate charge generating layerand a charge transport layer, the charge generation layer generallycomprises a binder in an amount from about 10 to about 90 weightpercent, in further embodiments from about 15 to about 80 weight percentand in some embodiments in an amount of from about 20 to about 75 weightpercent, based on the weight of the charge generation layer. Theoptional charge transport material in the charge generating layer, ifpresent, generally can be in an amount of at least about 2.5 weightpercent, in further embodiments from about 4 to about 30 weight percentand in other embodiments in an amount from about 10 to about 25 weightpercent, based on the weight of the charge generating layer. The chargetransport layer generally comprises a binder in an amount from about 20weight percent to about 70 weight percent and in further embodiments inan amount from about 30 weight percent to about 50 weight percent. Aperson of ordinary skill in the art will recognize that additionalranges of binder concentrations for the dual layer embodiments withinthe explicit ranges above are contemplated and are within the presentdisclosure.

For the embodiments with a single layer having a charge generatingcompound and a charge transport material, the photoconductive layergenerally comprises a binder, a charge transport material, and a chargegeneration compound. The charge generation compound can be in an amountfrom about 0.05 to about 25 weight percent and in further embodiment inan amount from about 2 to about 15 weight percent, based on the weightof the photoconductive layer. The charge transport material can be in anamount from about 10 to about 80 weight percent, in other embodimentsfrom about 25 to about 65 weight percent, in additional embodiments fromabout 30 to about 60 weight percent and in further embodiments in anamount from about 35 to about 55 weight percent, based on the weight ofthe photoconductive layer, with the remainder of the photoconductivelayer comprising the binder, and optionally additives, such as anyconventional additives. A single layer with a charge transportcomposition and a charge generating compound generally comprises abinder in an amount from about 10 weight percent to about 75 weightpercent, in other embodiments from about 20 weight percent to about 60weight percent, and in further embodiments from about 25 weight percentto about 50 weight percent. Optionally, the layer with the chargegenerating compound and the charge transport material may comprise asecond charge transport material. The optional second charge transportmaterial, if present, generally can be in an amount of at least about2.5 weight percent, in further embodiments from about 4 to about 30weight percent and in other embodiments in an amount from about 10 toabout 25 weight percent, based on the weight of the photoconductivelayer. A person of ordinary skill in the art will recognize thatadditional composition ranges within the explicit compositions rangesfor the layers above are contemplated and are within the presentdisclosure.

In general, any layer with an electron transport layer canadvantageously further include a UV light stabilizer. In particular, theelectron transport layer generally can comprise an electron transportcompound, a binder, and an optional UV light stabilizer. An overcoatlayer comprising an electron transport compound is described further incopending U.S. patent application Ser. No. 10/396,536 to Zhu et al.entitled, “Organophotoreceptor With An Electron Transport Layer,”incorporated herein by reference. For example, an electron transportcompound as described above may be used in the release layer of thephotoconductors described herein. The electron transport compound in anelectron transport layer can be in an amount from about 10 to about 50weight percent, and in other embodiments in an amount from about 20 toabout 40 weight percent, based on the weight of the electron transportlayer. A person of ordinary skill in the art will recognize thatadditional ranges of compositions within the explicit ranges arecontemplated and are within the present disclosure.

The UV light stabilizer, if present, in any one or more appropriatelayers of the photoconductor generally is in an amount from about 0.5 toabout 25 weight percent and in some embodiments in an amount from about1 to about 10 weight percent, based on the weight of the particularlayer. A person of ordinary skill in the art will recognize thatadditional ranges of compositions within the explicit ranges arecontemplated and are within the present disclosure.

For example, the photoconductive layer may be formed by dispersing ordissolving the components, such as one or more of a charge generatingcompound, the charge transport material of this invention, a secondcharge transport material such as a charge transport compound or anelectron transport compound, a UV light stabilizer, and a polymericbinder in organic solvent, coating the dispersion and/or solution on therespective underlying layer and drying the coating. In particular, thecomponents can be dispersed by high shear homogenization, ball-milling,attritor milling, high energy bead (sand) milling or other sizereduction processes or mixing means known in the art for effectingparticle size reduction in forming a dispersion.

The photoreceptor may optionally have one or more additional layers aswell. An additional layer can be, for example, a sub-layer or anovercoat layer, such as a barrier layer, a release layer, a protectivelayer, or an adhesive layer. A release layer or a protective layer mayform the uppermost layer of the photoconductor element. A barrier layermay be sandwiched between the release layer and the photoconductiveelement or used to overcoat the photoconductive element. The barrierlayer provides protection from abrasion to the underlayers. An adhesivelayer locates and improves the adhesion between a photoconductiveelement, a barrier layer and a release layer, or any combinationthereof. A sub-layer is a charge blocking layer and locates between theelectrically conductive substrate and the photoconductive element. Thesub-layer may also improve the adhesion between the electricallyconductive substrate and the photoconductive element.

Suitable barrier layers include, for example, coatings such ascrosslinkable siloxanol-colloidal silica coating and hydroxylatedsilsesquioxane-colloidal silica coating, and organic binders such aspolyvinyl alcohol, methyl vinyl ether/maleic anhydride copolymer,casein, polyvinyl pyrrolidone, polyacrylic acid, gelatin, starch,polyurethanes, polyimides, polyesters, polyamides, polyvinyl acetate,polyvinyl chloride, polyvinylidene chloride, polycarbonates, polyvinylbutyral, polyvinyl acetoacetal, polyvinyl formal, polyacrylonitrile,polymethyl methacrylate, polyacrylates, polyvinyl carbazoles, copolymersof monomers used in the above-mentioned polymers, vinyl chloride/vinylacetate/vinyl alcohol terpolymers, vinyl chloride/vinyl acetate/maleicacid terpolymers, ethylene/vinyl acetate copolymers, vinylchloride/vinylidene chloride copolymers, cellulose polymers, andmixtures thereof. The above barrier layer polymers optionally maycontain small inorganic particles such as fumed silica, silica, titania,alumina, zirconia, or a combination thereof. Barrier layers aredescribed further in U.S. Pat. No. 6,001,522 to Woo et al., entitled“Barrier Layer For Photoconductor Elements Comprising An Organic PolymerAnd Silica,” incorporated herein by reference. The release layer topcoatmay comprise any release layer composition known in the art. In someembodiments, the release layer is a fluorinated polymer, siloxanepolymer, fluorosilicone polymer, silane, polyethylene, polypropylene,polyacrylate, or a combination thereof. The release layers can comprisecrosslinked polymers.

The release layer may comprise, for example, any release layercomposition known in the art. In some embodiments, the release layercomprises a fluorinated polymer, siloxane polymer, fluorosiliconepolymer, polysilane, polyethylene, polypropylene, polyacrylate,poly(methyl methacrylate-co-methacrylic acid), urethane resins,urethane-epoxy resins, acrylated-urethane resins, urethane-acrylicresins, or a combination thereof. In further embodiments, the releaselayers comprise crosslinked polymers.

The protective layer can protect the organophotoreceptor from chemicaland mechanical degradation. The protective layer may comprise anyprotective layer composition known in the art. In some embodiments, theprotective layer is a fluorinated polymer, siloxane polymer,fluorosilicone polymer, polysilane, polyethylene, polypropylene,polyacrylate, poly(methyl methacrylate-co-methacrylic acid), urethaneresins, urethane-epoxy resins, acrylated-urethane resins,urethane-acrylic resins, or a combination thereof. In some embodimentsof particular interest, the release layers are crosslinked polymers.

An overcoat layer may comprise an electron transport compound asdescribed further in copending U.S. patent application Ser. No.10/396,536, filed on Mar. 25, 2003 to Zhu et al. entitled,“Organoreceptor With An Electron Transport Layer,” incorporated hereinby reference. For example, an electron transport compound, as describedabove, may be used in the release layer of this invention. The electrontransport compound in the overcoat layer can be in an amount from about2 to about 50 weight percent, and in other embodiments in an amount fromabout 10 to about 40 weight percent, based on the weight of the releaselayer. A person of ordinary skill in the art will recognize thatadditional ranges of composition within the explicit ranges arecontemplated and are within the present disclosure.

Generally, adhesive layers comprise a film forming polymer, such aspolyester, polyvinylbutyral, polyvinylpyrolidone, polyurethane,polymethyl methacrylate, poly(hydroxy amino ether) and the like. Barrierand adhesive layers are described further in U.S. Pat. No. 6,180,305 toAckley et al., entitled “Organic Photoreceptors for LiquidElectrophotography,” incorporated herein by reference.

Sub-layers can comprise, for example, polyvinylbutyral, organosilanes,hydrolyzable silanes, epoxy resins, polyesters, polyamides,polyurethanes, silicones, and the like. In some embodiments, thesub-layer has a dry thickness between about 20 Angstroms and about 2,000Angstroms. Sublayers containing metal oxide conductive particles can bebetween about 1 and about 25 microns thick. A person of ordinary skillin the art will recognize that additional ranges of compositions andthickness within the explicit ranges are contemplated and are within thepresent disclosure.

The charge transport materials as described herein, and photoreceptorsincluding these compounds, are suitable for use in an imaging processwith either dry or liquid toner development. For example, any dry tonersand liquid toners known in the art may be used in the process and theapparatus of this invention. Liquid toner development can be desirablebecause it offers the advantages of providing higher resolution imagesand requiring lower energy for image fixing compared to dry toners.Examples of suitable liquid toners are known in the art. Liquid tonersgenerally comprise toner particles dispersed in a carrier liquid. Thetoner particles can comprise a colorant/pigment, a resin binder, and/ora charge director. In some embodiments of liquid toner, a resin topigment ratio can be from 1:1 to 10:1, and in other embodiments, from4:1 to 8:1. Liquid toners are described further in Published U.S. PatentApplications 2002/0128349, entitled “Liquid Inks Comprising A StableOrganosol,” 2002/0086916, entitled “Liquid Inks Comprising TreatedColorant Particles,” and 2002/0197552, entitled “Phase Change DeveloperFor Liquid Electrophotography,” all three of which are incorporatedherein by reference.

Charge Transport Material

As described herein, an organophotoreceptor comprises a charge transportmaterial having the formula

where n is an integer between 2 and 6, inclusive;

-   -   R₁ and R₂ are, independently, H, halogen, carboxyl, hydroxyl,        thiol, cyano, nitro, aldehyde group, ketone group, an ether        group, an ester group, a carbonyl group, an alkyl group, an        alkaryl group, or an aryl group;    -   X is a linking group having the formula —(CH₂)_(m)—, branched or        linear, where m is an integer between 0 and 20, inclusive, and        one or more of the methylene groups can be optionally replaced        by O, S, C═O, O═S═O, a heterocyclic group, an aromatic group,        urethane, urea, an ester group, a NR₃ group, a CHR₄ group, or a        CR₅R₆ group where R₃, R₄, R₅, and R₆ are, independently, H, an        alkyl group, an alkaryl group, a heterocyclic group, or an aryl        group;    -   Y is a bond, C, N, O, S, a branched or linear —(CH₂)_(p)— group        where p is an integer between 0 and 10 and where one or more of        the hydrogen atoms in the —(CH₂)_(p)— may be optionally removed        to provide bond positions to enable n to have a higher value        than 2, an aromatic group, a cycloalkyl group, a heterocyclic        group, or a NR₇ group where R₇ is hydrogen atom, an alkyl group,        or aryl group; and    -   Z is a fluorenylidene group.

Specific, non-limiting examples of suitable charge transport materialswithin the general Formula (1) of the present invention have thefollowing structures:

Synthesis of Charge Transport Materials

The synthesis of the charge transport materials of this invention can beprepared by a 3-step synthesis procedure. The first step is the reactionof 9-fluorenone-4-carbonyl chloride or its derivative with a dihydroxylcompound, a dithiol compound, or a diamino compound in a solvent,optionally with a catalytical amount of a trialkylamine, to form adimeric fluorenone derivative. The second step is the preparation of afluorenone hydrazone derivative by the reaction of hydrazine with afluorenone derivative. The last step is the reaction of the dimericfluorenone derivative with the fluorenone hydrazone derivative in 1:2mole ratio under acidic condition to form a dimericbis(9-fluorenone)azine derivative.

The invention will now be described further by way of the followingexamples.

EXAMPLES Example 1 Synthesis and Characterization Charge TransportMaterials

This example described the synthesis and characterization of Compounds2-8 in which the numbers refer to formula numbers above. Thecharacterization involves both chemical characterization and theelectronic characterization of materials formed with the compound.

Preparation of (4-n-Butoxycarbonyl-9-fluorenylidene)malononitrile

A 70 g (0.312 mole) quantity of fluorenone-4-carboxylic acid(commercially available from Aldrich, Milwaukee, Wis.), 480 g (6.5 mole)of n-butanol (commercially obtained from Fisher Scientific Company Inc.,Hanover Park, Ill.), 1000 ml of toluene and 4 ml of concentratedsulfuric acid were added to a 2-liter round bottom flask equipped with amechanical stirrer and a reflux condenser with a Dean Stark apparatus.The solution was refluxed for 5 hours with aggressive agitation andrefluxing, during which about 6 g of water were collected in the DeanStark apparatus. The flask was cooled to room temperature. The solventswere evaporated, and the residue was added to 4-liter of 3% sodiumbicarbonate aqueous solution with agitation. The solid was filtered off,washed with water until the pH of the water was neutral, and dried inthe hood overnight. The product was n-butyl fluorenone-4-carboxylateester (70 g, 80% yield). A ¹H-NMR spectrum of n-butylfluorenone-4-carboxylate ester was obtained in CDCl₃ with a 300 MHz NMRfrom Bruker Instrument. The peaks were found at (ppm) δ=0.87-1.09 (t,3H); δ=1.42-1.70 (m, 2H); δ=1.75-1.88 (q, 2H); δ=4.26-4.64 (t, 2H);δ=7.29-7.45 (m, 2H); δ=7.46-7.58 (m, 1H); δ=7.60-7.68 (dd, 1H);δ=7.75-7.82 (dd, 1H); δ=7.90-8.00 (dd, 1H); δ=8.25-8.35 (dd, 1H).

A 70 g (0.25 mole) of n-butyl fluorenone-4-carboxylate ester, 750 ml ofabsolute methanol, 37 g (0.55 mole) of malononitrile (commerciallyobtained from Sigma-Aldrich, Milwaukee, Wis.) and 20 drops of piperidine(commercially obtained from Sigma-Aldrich, Milwaukee, Wis.) were addedto a 2-liter, 3-neck round bottom flask equipped with a mechanicalstirrer and a reflux condenser. The solution was refluxed for 8 hours,and the flask was cooled to room temperature. An orange crude productwas filtered, washed twice with 70 ml of methanol and once with 150 mlof water, and dried in the hood for overnight. This orange crude productwas recrystallized from a mixture of 600 ml of acetone and 300 ml ofmethanol using activated charcoal. The flask was placed at 0° C. for 16hours. The crystals were filtered and dried in a vacuum oven at 50° C.for 6 hours to obtain 60 g of pure(4-n-butoxycarbonyl-9-fluorenylidene)malononitrile. The melting point ofthe product was 99-100° C. A ¹H-NMR spectrum of(4-n-butoxycarbonyl-9-fluorenylidene) malononitrile was obtained inCDCl₃ with a 300 MHz NMR from Bruker Instrument. The peaks were found at(ppm) δ=0.74-1.16 (t, 3H); δ=1.38-1.72 (m, 2H); δ=1.70-1.90 (q, 2H);δ=4.29-4.55 (t, 2H); δ=7.31-7.43 (m, 2H); δ=7.45-7.58 (m, 1H);δ=7.81-7.91 (dd, 1H); δ=8.15-8.25 (dd, 1H); δ=8.42-8.52 (dd, 1H);δ=8.56-8.66 (dd, 1H).

Preparation of Ethyl 9-Fluorenone-4-Carboxylate Ester

A 70 g (0.312 mole) quantity of 9-fluorenone-4-carboxylic acid(commercially obtained from Aldrich Chemicals, Milwaukee, Wis.), 300 gof ethyl alcohol (6.5 mole, commercially obtained from AldrichChemicals, Milwaukee, Wis.), 1000 ml of toluene, and 4 ml ofconcentrated sulfuric acid were added to a 2-liter round bottom flaskequipped with a mechanical stirrer and a reflux condenser with a DeanStark apparatus. With aggressive agitation and refluxing, the solutionwas refluxed for 5 hours, during which time about 6 g of water werecollected in the Dean Stark apparatus. The flask was cooled to roomtemperature. The solvents were evaporated, and the residue was added,with agitation, to 4-liters of a 3% sodium bicarbonate aqueous solution.The solid was filtered off, washed with water until the pH of thewash-water was neutral, and dried in the hood overnight. The product wasethyl 9-fluorenone-4-carboxylate ester. The yield was 65 g (83%). A¹H-NMR spectrum of ethyl 9-fluorenone-4-carboxylate ester was obtainedin CDCl₃ with a 300 MHz NMR from Bruker Instrument. The peaks for thealiphatic region were found at (ppm) δ=1.38-1.53 (t, 3H); δ=4.40-4.59(q, 2H). The aromatic region has several peaks at δ=7.30-8.33.

Preparation of Ethyl 9-Fluorenone-4-Carboxylate Ester Hydrazone

A 50.45 g quantity of ethyl 9-fluorenone-4-carboxylate ester (0.2 mole,prepared previously) and 200 ml of ethanol, 12.82 g of anhydroushydrazine (0.4 mole, obtained from Aldrich Chemicals, Milwaukee, Wis.)were added to a 500 ml, 3-neck round bottom flask equipped with amechanical stirrer and a reflux condenser. The flask was heated at 74°C. for 5 hours. The solution was kept at 0° C. for overnight. A yellowsolid was filtered off, washed with 50 ml of ethanol, and dried at 50°C. in a vacuum oven for 8 hours. The yield of ethyl9-fluorenone-4-carboxylate ester hydrazone was 40 g (76%). A ¹H-NMRspectrum in CDCl₃ yielded chemical shifts (ppm) (using a 300 MHz H-NMRBruker instrument) as follows: Aliphatic protons: δ=1.38-1.53 (t, 3H);δ=4.40-4.59 (q, 2H). The NH₂ has two broad singlets at δ=6.35-6.61. Thearomatic protons appeared in the range of δ=7.28-8.52.

Preparation of n-Butyl 9-fluorenone-4-carboxylate Ester

A 70 g (0.312 mole) quantity of 9-fluorenone-4-carboxylic acid, 480 g(6.5 mole) of n-butanol (commercially obtained from Fisher ScientificCompany Inc., Hanover Park, Ill.), 1000 ml of toluene and 4 ml ofconcentrated sulfuric acid were added to a 2-liter round bottom flaskequipped with a mechanical stirrer and a reflux condenser with a DeanStark apparatus. The solution was refluxed for 5 hours with aggressiveagitation and refluxing, during which about 6 g of water were collectedin the Dean Stark apparatus. The flask was cooled to room temperature.The solvents were evaporated, and the residue was added to 4-liters of3% sodium bicarbonate aqueous solution with agitation. The solid wasfiltered off, washed with water until the pH of the water was neutral,and dried in the hood overnight. The product was n-butyl9-fluorenone-4-carboxylate ester (70 g, 80% yield). A ¹H-NMR spectrum ofn-butyl 9-fluorenone-4-carboxylate ester was obtained in CDCl₃ with a300 MHz NMR from Bruker Instrument. The peaks were found at (ppm)δ=0.87-1.09 (t, 3H); δ=1.42-1.70 (m, 2H); δ=1.75-1.88 (q, 2H);δ=4.26-4.64 (t, 2H); δ=7.29-7.45 (m, 2H); δ=7.46-7.58 (m, 1H);δ=7.60-7.68 (dd, 1H); δ=7.75-7.82 (dd, 1H); δ=7.90-8.00 (dd, 1H);δ=8.25-8.35 (dd, 1H).

Preparation of n-Butyl 9-Fluorenone-4-carboxylate Ester Hydrazone

A 56.0 g quantity of butyl 9-fluorenone-4-carboxylate ester (0.2 mole,prepared previously) and 200 ml of ethanol, 12.82 g of anhydroushydrazine (0.4 mole, obtained from Aldrich Chemicals, Milwaukee, Wis.)were added to a 500 ml, 3-neck round bottom flask equipped with amechanical stirrer and a reflux condenser. The flask was heated at 74°C. for 5 hours. The solution was kept at 0° C. for overnight. A yellowsolid was filtered off and washed with 50 ml of ethanol and dried at 50°C. in a vacuum oven for 8 hours. The yield of n-butyl9-fluorenone-4-carboxylate ester hydrazone was 49 g (83%). A ¹H-NMRspectrum in CDCl₃ yielded chemical shifts (ppm) (using 300 MHz H-NMRBruker instrument) as follows: Aliphatic protons: δ=0.9-1.11 (t, 3H);δ=1.40-1.63 (m, 2H); δ=1.71-1.90 (m, 2H); δ=4.36-4.50 (t, 2H). The NH₂has two broad singlets at δ=6.35-6.66. The aromatic protons appeared inthe range of δ=7.28-8.52.

Preparation of Compound (2)

A 10.0 g of 9-fluorenone-4-carbonyl chloride (0.04 mole, obtained fromAldrich Chemicals Co, Milwaukee, Wis. 53201, USA) and 100 ml oftetrahydrofuran (obtained from Aldrich) were added to a 250 ml, 3-neckround bottom flask equipped with a reflux condenser and a mechanicalstirrer. The solution was stirred for about ½ hour, then 5.16 g of4,4′-thiobisbenzenethiol (0.02 mole, obtained from Aldrich) in 50 ml oftetrahydrofuran were added, followed by the addition of 4.17 g oftriethylamine (0.04 mole, obtained from Aldrich). The solution wasrefluxed for 6 hours and filtered hot to remove triethylaminehydrochloride salt byproduct. The filtrate was evaporated to dryness toobtain the crude product. The crude product was recrystallized fromtetrahydrofuran/methanol with activated charcoal. The product was driedat 60° C. vacuum oven for 6 hours to yield a first dimeric fluorenonederivative, which was a yellow solid (6.85 g, 50% yield).

The first dimeric fluorenone derivative (5.0 g, 0.00754 mole, preparedin previous step) and 100 ml of tetrahydrofuran (THF) were added to a500 ml 3-neck round bottom flask equipped with a reflux condenser and amechanical stirrer. The flask was heated with a heating mantle until allsolid entered to solution. A solution of ethyl9-fluorenone-4-carboxylate ester hydrazone (4.03 g, 0.0151 mole) in 50ml of tetrahydrofuran was added to the flask followed by the addition of20 drops of 37% aqueous hydrochloric acid. The flask was refluxed for 5hours. Activated charcoal was added, and the solution was boiled forabout 5 minutes then filtered hot into a beaker that contains 500 ml ofethyl alcohol. The product was isolated and recrystallized fromTHF/ethyl alcohol with activated charcoal. The product was isolated anddried at 50° C. in a vacuum oven for 6 hours. The yield was 5.33 g(61%). A ¹H-NMR spectrum in CDCl₃ yielded chemical shifts (ppm) (using300 MHz H-NMR Bruker instrument) as follows: Aliphatic protons:δ=1.34-1.54 (t, 6H); δ=4.36-4.57 (q, 4H). Aromatic protons appeared inthe region δ=7.17-8.40.

Preparation of Compound (3)

The first dimeric fluorenone derivative (5.0 g, 0.00754 mole, preparedas in Compound 2) and 100 ml of tetrahydrofuran (THF) were added to a500 ml 3-neck round bottom flask equipped with a reflux condenser and amechanical stirrer. The flask was heated with a heating mantle until allsolid entered to solution. A solution of n-butyl9-fluorenone-4-carboxylate ester hydrazone (4.44 g, 0.0151 mole) in 50ml of tetrahydrofuran was added to the flask, followed by the additionof 20 drops of 37% aqueous hydrochloric acid. The flask was refluxed for5 hours. Activated charcoal was added, and the solution was boiled forabout 5 minutes and then filtered hot into a beaker that contained 500ml of ethyl alcohol. The product was isolated and recrystallized fromTHF/ethyl alcohol with activated charcoal. The product was isolated anddried at 50° C. in a vacuum oven for 6 hours. The yield was 5.76 g(53%). A ¹H-NMR spectrum in CDCl₃ yielded chemical shifts (ppm) (using300 MHz H-NMR Bruker instrument) as follows: Aliphatic protons:δ=0.86-1.10 (t, 6H); δ=1.37-1.65 (m, 4H); δ=1.69-1.90 (q, 4H);δ=4.36-4.49 (t, 4H). Aromatic protons appeared in the regionδ=7.17-8.42.

Preparation of Compound (4)

A 4.85 g quantity of 9-fluorenone-4-carbonyl chloride (0.02 mole,obtained from Aldrich Chemicals Co, Milwaukee, Wis. 53201, USA) and 100ml of tetrahydrofuran (obtained from Aldrich) were added to a 250 ml,3-neck round bottom flask equipped with a reflux condenser and amechanical stirrer. The solution was stirred for about ½ hour, and then1.74 g of 1,10-decanediol (0.01 mole, obtained from Aldrich) in 50 ml oftetrahydrofuran were added, followed by the addition of 2 g oftriethylamine (0.02 mole, obtained from Aldrich). The solution wasrefluxed for 6 hours and filtered hot to remove triethylaminehydrochloride salt by-product, and the filtrate was evaporated todryness. A liquid product was obtained, which solidified upon standingat room temperature for a couple of hours. The crude product wasrecrystallized from ethyl acetate with activated charcoal. The productwas dried at 60° C. in a vacuum oven for 6 hours to yield a seconddimeric fluorenone derivative, which was a yellow solid (2.5 g, 43%yield). The product had a melting point of 101-102° C. A ¹H-NMR spectrum(300 MHz) in CDCl₃ yielded chemical shifts (ppm) as follows: 1.15-1.61(m, 12H); 1.71-1.92 (q, 4H); 4.34-4.47 (t, 4H); 7.32-7.37 (m, 4H); 7.50(td, 2H); 7.70 (d, 2H); 7.82 (dd, 2H); 7.93 (dd, 2H); 8.28 (d, 2H).

Compound (4) can be obtained by reacting the second dimeric fluorenonederivative with ethyl 9-fluorenone-4-carboxylate ester hydrazone undersimilar conditions as those used for obtaining Compound (2).

Preparation of Compound (5)

A 10.0 g quantity of 9-fluorenone-4-carbonyl (0.04 mole, obtained fromAldrich Chemicals Co, Milwaukee, Wis. 53201, USA) and 100 ml oftetrahydrofuran (obtained from Aldrich) were added to a 250 ml, 3-neckround bottom flask equipped with a reflux condenser and a mechanicalstirrer. The solution was stirred for about ½ hour and then 2.186 g ofdiethylene glycol (0.02 mole, obtained from Aldrich) in 50 ml oftetrahydrofuran were added, followed by the addition of 4.17 g oftriethylamine (0.04 mole, obtained from Aldrich). The solution wasrefluxed for 6 hours and filtered hot to remove triethylaminehydrochloride salt byproduct, and the filtrate was evaporated to drynessto obtain the crude product. The crude product was recrystallized fromethyl acetate with activated charcoal. The product was dried at 60° C.in a vacuum oven for 6 hours to yield a third dimeric fluorenonederivative, which was a yellow solid (5.0 g, 47% yield). The product hada melting point of 137° C. A ¹H-NMR (300 MHz) spectrum in CDCl₃ yieldedchemical shifts (ppm) as follows: 3.88-4.00 (t, 4H); 4.56-4.65 (t, 4H);7.15-7.34 (m, 4H); 7.40-7.49 (td, 2H); 7.61-7.68 (d, 2H); 7.71-7.77 (dd,2H); 7.85-7.92 (dd, 2H); 8.20-8.27 (d, 2H).

Compound (5) can be obtained by reacting the third dimeric fluorenonederivative with ethyl 9-fluorenone-4-carboxylate ester hydrazone undersimilar conditions used for obtaining Compound (2).

Preparation of Compound (6)

A 10.0 g quantity of 9-fluorenone-4-carbonyl (0.04 mole, obtained fromAldrich Chemicals Co, Milwaukee, Wis. 53201, USA) and 100 ml oftetrahydrofuran (obtained from Aldrich) were added to a 250 ml, 3-neckround bottom flask equipped with a reflux condenser and a mechanicalstirrer. The solution was stirred for about ½ hour, and then 9.04 g of4,4′-(9-fluorenylidene)bis(2-phenoxyethanol) (0.02 mole, obtained fromAldrich) in 50 ml of tetrahydrofuran were added, followed by theaddition of 4.17 g of triethylamine (0.04 mole, obtained from Aldrich).The solution was refluxed for 6 hours and filtered hot to removetriethylamine hydrochloride salt byproduct, and the filtrate wasevaporated to dryness to obtain the crude product. The crude product wasrecrystallized from tetrahydrofuran with activated charcoal. The productwas dried at 60° C. in a vacuum oven for 6 hours to yield a fourthdimeric fluorenone derivative, which was a yellow solid (9.0 g, 51%yield). The product had a melting point from 137-138° C. A ¹H-NMR (300MHz) spectrum in CDCl₃ yielded chemical shifts (ppm) as follows:4.25-4.34 (t, 4H); 4.67-4.77 (t, 4H); 6.71-6.86 (m, 4H); 7.06-7.17 (m,4H); 7.19-7.48 (m, 12H); 7.65-7.72 (td, 2H); 7.72-7.79 (d, 2H);7.78-7.84 (dd, 2H); 7.86-7.95 (dd, 2H); 8.22-8.33 (d, 2H).

Compound (6) can be obtained by reacting the fourth dimeric fluorenonederivative with ethyl 9-fluorenone-4-carboxylate ester hydrazone undersimilar conditions used for obtaining Compound (2).

Preparation of Compound (7)

A 10.0 g quantity of 9-fluorenone-4-carbonyl (0.04 mole, obtained fromAldrich Chemicals Co, Milwaukee, Wis. 53201, USA) and 100 ml oftetrahydrofuran (obtained from Aldrich) were added to a 250 ml, 3-neckround bottom flask equipped with a reflux condenser and a mechanicalstirrer. The solution was stirred for about ½ hour, and then 6.97 g ofbis [4-(2-hydroxyethoxy)phenyl]sulfone (0.02 mole, obtained fromAldrich) in 50 ml of tetrahydrofuran were added, followed by theaddition of 4.17 g of triethylamine (0.04 mole, obtained from Aldrich).The solution was refluxed for 6 hours and filtered hot to removetriethylamine hydrochloride salt byproduct, and the filtrate wasevaporated to dryness to obtain the crude product. The crude product wasrecrystallized from tetrahydrofuran with activated charcoal. The productwas dried at 60° C. in a vacuum oven for 6 hours to yield a fifthdimeric fluorenone derivative, which was a yellow solid (9.3 g, 60%yield). A ¹H-NMR spectrum (300 MHz) in CDCl₃ yielded chemical shifts(ppm) as follows: 4.35-4.43 (t, 4H); 4.72-4.81 (t, 4H); 6.95-7.05 (m,4H); 7.27-7.38 (m, 4H); 7.40-7.52 (dd, 2H); 7.66-7.74 (dd, 2H);7.79-7.94 (m, 8H); 8.25-8.33 (d, 2H).

Compound (7) can be obtained by reacting the fifth dimeric fluorenonederivative with ethyl 9-fluorenone-4-carboxylate ester hydrazone undersimilar conditions used for obtaining Compound (2).

Preparation of Compound (8)

A sixth dimeric fluorenone derivative can be prepared similarly usingthe procedure used for the preparation of the first dimeric fluorenonederivative, which was prepared for the formation of Compound (2), exceptthat 4,4′-thiobisbenzenethiol is replaced by2,5-dimecapto-1,3,4-thiadiazole (Aldrich, Milwaukee, Wis.).

Compound (8) can be obtained by reacting the sixth dimeric fluorenonederivative with ethyl 9-fluorenone-4-carboxylate ester hydrazone undersimilar conditions used for obtaining Compound (2).

Example 2 Preparation of Organophotoreceptors

Comparative Sample A

Comparative Sample A was a single layer organophotoreceptor coated on a30 mm diameter anodized aluminum drum substrate. The coating solutionfor the single layer organophotoreceptor was prepared by pre-mixing 2.4g of 20 weight % (4-n-butoxycarbonyl-9-fluorenylidene)malononitrile intetrahydrofuran, 6.66 g of 25 weight % MPCT-10 (a charge transfermaterial, commercially obtained from Mitsubishi Paper Mills, Tokyo,Japan) in tetrahydrofuran, 7.65 g of 12 weight % polyvinyl butyral resin(BX-1, commercially obtained from Sekisui Chemical Co. Ltd., Japan) intetrahydrofuran. A 0.74 g quantity of a CGM mill-base containing 19weight % of titanyl oxyphthalocyanine and a polyvinyl butyral resin(BX-5, commercially obtained from Sekisui Chemical Co. Ltd., Japan) at aweight ratio of 7:3 was then added to the above mixture. The CGMmill-base was obtained by milling 112.7 g of titanyl oxyphthalocyanine(commercially obtained from H.W. Sands Corp., Jupiter, Fla.) with 49 gof the polyvinyl butyral resin (BX-5) in 651 g of methylethylketone on ahorizontal sand mill (model LMC12 DCMS, commercially obtained fromNetzsch Incorporated, Exton, Pa.) with 1-micron zirconium beads usingrecycle mode for 4 hours. After mixing on a mechanical shaker for about1 hour, the single layer coating solution was ring coated onto the 30 mmdiameter anodized aluminum drum at a rate of about 175 mm/min. Thecoated drum was dried in an oven at 110° C. for 5-10 minutes. The dryphotoconductor film thickness was 12μ±0.5μ.

Comparative Sample B

Comparative Sample B was a single layer organophotoreceptor coated on a30 mm diameter anodized aluminum drum substrate. The coating solutionfor the single layer organophotoreceptor was prepared by pre-mixing 2.4g of 20 weight % (4-n-butoxycarbonyl-9-fluorenylidene)malononitrile intetrahydrofuran, 6.66 g of 25 weight % MPCT-10 (a charge transfermaterial, commercially obtained from Mitsubishi Paper Mills, Tokyo,Japan) in tetrahydrofuran, 7.65 g of 12 weight % polyvinyl butyral resin(BX-1, commercially obtained from Sekisui Chemical Co. Ltd., Japan) intetrahydrofuran. A 0.74 g quantity of a CGM mill-base containing 19weight % of titanyl oxyphthalocyanine and a polyvinyl butyral resin(BX-5, commercially obtained from Sekisui Chemical Co. Ltd., Japan) at aweight ratio of 7:3 was then added to the above mixture. The CGMmill-base was obtained by milling 112.7 g of titanyl oxyphthalocyanine(commercially obtained from H.W. Sands Corp., Jupiter, Fla.) with 49 gof the polyvinyl butyral resin (BX-5) in 651 g of methylethylketone on ahorizontal sand mill (model LMC12 DCMS, commercially obtained fromNetzsch Incorporated, Exton, Pa.) with 1-micron zirconium beads usingrecycle mode for 4 hours. After mixing on a mechanical shaker for about1 hour, the single layer coating solution was ring coated onto the 30 mmdiameter anodized aluminum drum at a rate of about 230 mm/min. Thecoated drum was dried in an oven at 110° C. for 5-10 minutes. The dryphotoconductor film thickness was 15μ±0.5μ.

Comparative Sample C

Comparative Sample C was a single layer organophotoreceptor coated on a30 mm diameter anodized aluminum drum substrate. The coating solutionfor the single layer organophotoreceptor was prepared by pre-mixing 2.4g of 20 weight % (4-n-butoxycarbonyl-9-fluorenylidene)malononitrile intetrahydrofuran, 6.66 g of 25 weight % MPCT-10 (a charge transfermaterial, commercially obtained from Mitsubishi Paper Mills, Tokyo,Japan) in tetrahydrofuran, 7.65 g of 12 weight % polyvinyl butyral resin(BX-1, commercially obtained from Sekisui Chemical Co. Ltd., Japan) intetrahydrofuran. A 0.74 g quantity of a CGM mill-base containing 19weight % of titanyl oxyphthalocyanine and a polyvinyl butyral resin(BX-5, commercially obtained from Sekisui Chemical Co. Ltd., Japan) at aweight ratio of 7:3 was then added to the above mixture. The CGMmill-base was obtained by milling 112.7 g of titanyl oxyphthalocyanine(commercially obtained from H.W. Sands Corp., Jupiter, Fla.) with 49 gof the polyvinyl butyral resin (BX-5) in 651 g of methylethylketone on ahorizontal sand mill (model LMC12 DCMS, commercially obtained fromNetzsch Incorporated, Exton, Pa.) with 1-micron zirconium beads usingrecycle mode for 4 hours. After mixing on a mechanical shaker for about1 hour, the single layer coating solution was ring coated onto the 30 mmdiameter anodized aluminum drum at a rate of about 360 mm/min. Thecoated drum was dried in an oven at 110° C. for 5-10 minutes. The dryphotoconductor film thickness was 22μ±0.5μ.

Sample 1

Sample 1 was a single layer organophotoreceptor coated on a 30 mmdiameter anodized aluminum drum substrate. The coating solution for thesingle layer organophotoreceptor was prepared by pre-mixing 2.4 g of 20weight % Compound (3) in 1,1,2-trichloroethane, 6.66 g of 25 weight %MPCT-10 (a charge transfer material, commercially obtained fromMitsubishi Paper Mills, Tokyo, Japan) in tetrahydrofuran, 7.65 g of 12weight % polyvinyl butyral resin (BX-1, commercially obtained fromSekisui Chemical Co. Ltd., Japan) in tetrahydrofuran. A 0.74 g quantityof a CGM mill-base containing 19 weight % of titanyl oxyphthalocyanineand a polyvinyl butyral resin (BX-5, commercially obtained from SekisuiChemical Co. Ltd., Japan) at a weight ratio of 7:3 was then added to theabove mixture. The CGM mill-base was obtained by milling 112.7 g oftitanyl oxyphthalocyanine (commercially obtained from H.W. Sands Corp.,Jupiter, Fla.) with 49 g of the polyvinyl butyral resin (BX-5) in 651 gof methylethylketone on a horizontal sand mill (model LMC12 DCMS,commercially obtained from Netzsch Incorporated, Exton, Pa.) with1-micron zirconium beads using recycle mode for 4 hours. After mixing ona mechanical shaker for about 1 hour, the single layer coating solutionwas ring coated onto the 30 mm diameter anodized aluminum drum at a rateof about 175 mm/min. The coated drum was dried in an oven at 110° C. for5-10 minutes. The dry photoconductor film thickness was 12μ±0.5μ.

Sample 2

Sample 2 was a single layer organophotoreceptor coated on a 30 mmdiameter anodized aluminum drum substrate. The coating solution for thesingle layer organophotoreceptor was prepared by pre-mixing 2.4 g of 20weight % Compound (3) in 1,1,2-trichloroethane, 6.66 g of 25 weight %MPCT-10 (a charge transfer material, commercially obtained fromMitsubishi Paper Mills, Tokyo, Japan) in tetrahydrofuran, 7.65 g of 12weight % polyvinyl butyral resin (BX-1, commercially obtained fromSekisui Chemical Co. Ltd., Japan) in tetrahydrofuran. A 0.74 g quantityof a CGM mill-base containing 19 weight % of titanyl oxyphthalocyanineand a polyvinyl butyral resin (BX-5, commercially obtained from SekisuiChemical Co. Ltd., Japan) at a weight ratio of 7:3 was then added to theabove mixture. The CGM mill-base was obtained by milling 112.7 g oftitanyl oxyphthalocyanine (commercially obtained from H.W. Sands Corp.,Jupiter, Fla.) with 49 g of the polyvinyl butyral resin (BX-5) in 651 gof methylethylketone on a horizontal sand mill (model LMC12 DCMS,commercially obtained from Netzsch Incorporated, Exton, Pa.) with1-micron zirconium beads using recycle mode for 4 hours. After mixing ona mechanical shaker for about 1 hour, the single layer coating solutionwas ring coated onto the 30 mm diameter anodized aluminum drum at a rateof about 210 mm/min. The coated drum was dried in an oven at 110° C. for5-10 minutes. The dry photoconductor film thickness was 14μ±0.5μ.

Sample 3

Sample 3 was a single layer organophotoreceptor coated on a 30 mmdiameter anodized aluminum drum substrate. The coating solution for thesingle layer organophotoreceptor was prepared by pre-mixing 2.4 g of 20weight % Compound (3) in 1,1,2-trichloroethane, 6.66 g of 25 weight %MPCT-10 (a charge transfer material, commercially obtained fromMitsubishi Paper Mills, Tokyo, Japan) in tetrahydrofuran, 7.65 g of 12weight % polyvinyl butyral resin (BX-1, commercially obtained fromSekisui Chemical Co. Ltd., Japan) in tetrahydrofuran. A 0.74 g quantityof a CGM mill-base containing 19 weight % of titanyl oxyphthalocyanineand a polyvinyl butyral resin (BX-5, commercially obtained from SekisuiChemical Co. Ltd., Japan) at a weight ratio of 7:3 was then added to theabove mixture. The CGM mill-base was obtained by milling 112.7 g oftitanyl oxyphthalocyanine (commercially obtained from H.W. Sands Corp.,Jupiter, Fla.) with 49 g of the polyvinyl butyral resin (BX-5) in 651 gof methylethylketone on a horizontal sand mill (model LMC12 DCMS,commercially obtained from Netzsch Incorporated, Exton, Pa.) with1-micron zirconium beads using recycle mode for 4 hours. After mixing ona mechanical shaker for about 1 hour, the single layer coating solutionwas ring coated onto the 30 mm diameter anodized aluminum drum at a rateof about 230 mm/min. The coated drum was dried in an oven at 110° C. for5-10 minutes. The dry photoconductor film thickness was 15μ±0.5μ.

Sample 4

Sample 4 was a single layer organophotoreceptor coated on a 30 mmdiameter anodized aluminum drum substrate. The coating solution for thesingle layer organophotoreceptor was prepared by pre-mixing 2.4 g of 20weight % Compound (2) in 1,1,2-trichloroethane, 6.66 g of 25 weight %MPCT-10 (a charge transfer material, commercially obtained fromMitsubishi Paper Mills, Tokyo, Japan) in tetrahydrofuran, 7.65 g of 12weight % polyvinyl butyral resin (BX-1, commercially obtained fromSekisui Chemical Co. Ltd., Japan) in tetrahydrofuran. A 0.74 g quantityof a CGM mill-base containing 19 weight % of titanyl oxyphthalocyanineand a polyvinyl butyral resin (BX-5, commercially obtained from SekisuiChemical Co. Ltd., Japan) at a weight ratio of 7:3 was then added to theabove mixture. The CGM mill-base was obtained by milling 112.7 g oftitanyl oxyphthalocyanine (commercially obtained from H.W. Sands Corp.,Jupiter, Fla.) with 49 g of the polyvinyl butyral resin (BX-5) in 651 gof methylethylketone on a horizontal sand mill (model LMC12 DCMS,commercially obtained from Netzsch Incorporated, Exton, Pa.) with1-micron zirconium beads using recycle mode for 4 hours. After mixing ona mechanical shaker for about 1 hour, the single layer coating solutionwas ring coated onto the 30 mm diameter anodized aluminum drum at a rateof about 420 mm/min. The coated drum was dried in an oven at 110° C. for5-10 minutes. The dry photoconductor film thickness was 25μ±0.5μ.

Sample 5

Sample 5 was a single layer organophotoreceptor coated on a 30 mmdiameter anodized aluminum drum substrate. The coating solution for thesingle layer organophotoreceptor was prepared by pre-mixing 2.4 g of 20weight % Compound (3) in 1,1,2-trichloroethane, 6.66 g of 25 weight %MPCT-38 (a charge transfer material, commercially obtained fromMitsubishi Paper Mills, Tokyo, Japan) in tetrahydrofuran, 7.65 g of 12weight % polyvinyl butyral resin (BX-1, commercially obtained fromSekisui Chemical Co. Ltd., Japan) in tetrahydrofuran. A 0.74 g quantityof a CGM mill-base containing 19 weight % of titanyl oxyphthalocyanineand a polyvinyl butyral resin (BX-5, commercially obtained from SekisuiChemical Co. Ltd., Japan) at a weight ratio of 7:3 was then added to theabove mixture. The CGM mill-base was obtained by milling 112.7 g oftitanyl oxyphthalocyanine (commercially obtained from H.W. Sands Corp.,Jupiter, Fla.) with 49 g of the polyvinyl butyral resin (BX-5) in 651 gof methylethylketone on a horizontal sand mill (model LMC12 DCMS,commercially obtained from Netzsch Incorporated, Exton, Pa.) with1-micron zirconium beads using recycle mode for 4 hours. After mixing ona mechanical shaker for about 1 hour, the single layer coating solutionwas ring coated onto the 30 mm diameter anodized aluminum drum at a rateof about 195 mm/min. The coated drum was dried in an oven at 110° C. for5-10 minutes. The dry photoconductor film thickness was 13μ±0.5μ.

Sample 6

Sample 6 was a single layer organophotoreceptor coated on a 30 mmdiameter anodized aluminum drum substrate. The coating solution for thesingle layer organophotoreceptor was prepared by pre-mixing 2.4 g of 20weight % Compound (3) in 1,1,2-trichloroethane, 3.33 g of 25 weight %MPCT-10 (a charge transfer material, commercially obtained fromMitsubishi Paper Mills, Tokyo, Japan) in tetrahydrofuran, 3.33 g of 25weight % MPCT-38 (a charge transfer material, commercially obtained fromMitsubishi Paper Mills, Tokyo, Japan) in tetrahydrofuran, 7.65 g of 12weight % polyvinyl butyral resin (BX-1, commercially obtained fromSekisui Chemical Co. Ltd., Japan) in tetrahydrofuran. A 0.74 g quantityof a CGM mill-base containing 19 weight % of titanyl oxyphthalocyanineand a polyvinyl butyral resin (BX-5, commercially obtained from SekisuiChemical Co. Ltd., Japan) at a weight ratio of 7:3 was then added to theabove mixture. The CGM mill-base was obtained by milling 112.7 g oftitanyl oxyphthalocyanine (commercially obtained from H.W. Sands Corp.,Jupiter, Fla.) with 49 g of the polyvinyl butyral resin (BX-5) in 651 gof methylethylketone on a horizontal sand mill (model LMC12 DCMS,commercially obtained from Netzsch Incorporated, Exton, Pa.) with1-micron zirconium beads using recycle mode for 4 hours. After mixing ona mechanical shaker for about 1 hour, the single layer coating solutionwas ring coated onto the 30 mm diameter anodized aluminum drum at a rateof about 210 mm/min. The coated drum was dried in an oven at 110° C. for5-10 minutes. The dry photoconductor film thickness was 14μ±0.5μ.

Sample 7

Sample 7 was a single layer organophotoreceptor coated on a 30 mmdiameter anodized aluminum drum substrate. The coating solution for thesingle layer organophotoreceptor was prepared by pre-mixing 1.2 g of 20weight % Compound (3) in 1,1,2-trichloroethane, 1.2 g of 20 weight %ET400 (a hydroquinone derivative commercially available from TakasagoChemical Corp., Tokyo Japan) in THF, 3.33 g of 25 weight % MPCT-10 (acharge transfer material, commercially obtained from Mitsubishi PaperMills, Tokyo, Japan) in tetrahydrofuran, 3.33 g of 25 weight % MPCT-38(a charge transfer material, commercially obtained from Mitsubishi PaperMills, Tokyo, Japan) in tetrahydrofuran, 7.65 g of 12 weight % polyvinylbutyral resin (BX-1, commercially obtained from Sekisui Chemical Co.Ltd., Japan) in tetrahydrofuran. A 0.74 g quantity of a CGM mill-basecontaining 19 weight % of titanyl oxyphthalocyanine and a polyvinylbutyral resin (BX-5, commercially obtained from Sekisui Chemical Co.Ltd., Japan) at a weight ratio of 7:3 was then added to the abovemixture. The CGM mill-base was obtained by milling 112.7 g of titanyloxyphthalocyanine (commercially obtained from H.W. Sands Corp., Jupiter,Fla.) with 49 g of the polyvinyl butyral resin (BX-5) in 651 g ofmethylethylketone on a horizontal sand mill (model LMC12 DCMS,commercially obtained from Netzsch Incorporated, Exton, Pa.) with1-micron zirconium beads using recycle mode for 4 hours. After mixing ona mechanical shaker for about 1 hour, the single layer coating solutionwas ring coated onto the 30 mm diameter anodized aluminum drum at a rateof about 155 mm/min. The coated drum was dried in an oven at 110° C. for5-10 minutes. The dry photoconductor film thickness was 11μ±0.5μ.

Sample 8

Sample 8 was a single layer organophotoreceptor coated on a 30 mmdiameter anodized aluminum drum substrate. The coating solution for thesingle layer organophotoreceptor was prepared by pre-mixing 2.16 g of 20weight % Compound (3) in 1,1,2-trichloroethane, 0.24 g of 20 weight %ET400 (a hydroquinone derivative commercially available from TakasagoChemical Corp., Tokyo, Japan) in THF, 3.33 g of 25 weight % MPCT-10 (acharge transfer material, commercially obtained from Mitsubishi PaperMills, Tokyo, Japan) in tetrahydrofuran, 3.33 g of 25 weight % MPCT-38(a charge transfer material, commercially obtained from Mitsubishi PaperMills, Tokyo, Japan) in tetrahydrofuran, 7.65 g of 12 weight % polyvinylbutyral resin (BX-1, commercially obtained from Sekisui Chemical Co.Ltd., Japan) in tetrahydrofuran. A 0.74 g quantity of a CGM mill-basecontaining 19 weight % of titanyl oxyphthalocyanine and a polyvinylbutyral resin (BX-5, commercially obtained from Sekisui Chemical Co.Ltd., Japan) at a weight ratio of 7:3 was then added to the abovemixture. The CGM mill-base was obtained by milling 112.7 g of titanyloxyphthalocyanine (commercially obtained from H.W. Sands Corp., Jupiter,Fla.) with 49 g of the polyvinyl butyral resin (BX-5) in 651 g ofmethylethylketone on a horizontal sand mill (model LMC12 DCMS,commercially obtained from Netzsch Incorporated, Exton, Pa.) with1-micron zirconium beads using recycle mode for 4 hours. After mixing ona mechanical shaker for about 1 hour, the single layer coating solutionwas ring coated onto the 30 mm diameter anodized aluminum drum at a rateof about 210 mm/min. The coated drum was dried in an oven at 110° C. for5-10 minutes. The dry photoconductor film thickness was 14μ±0.5μ.

Example 3 Electrostatic Testing and Properties of Organophotoreceptors

This example provides results of electrostatic testing on theorganophotoreceptor samples formed as described in Example 1.

Electrostatic cycling performance of organophotoreceptors describedherein with bis(9-fluorenone)azine compounds can be determined usingin-house designed and developed test bed. Electrostatic evaluation onthe 30 mm drum test bed is designed to accelerate electrostatic fatigueduring extended cycling by increasing the charge-discharge cyclingfrequency and decreasing the recovery time as compared to drum test bedswith longer process speeds. The location of each station in the tester(distance and elapsed time per cycle) is given as follows.

Electrostatic test stations around the 30 mm drum at 12.7 cm/s. TotalDistance, Total Time, Station Degrees cm sec Erase Bar Center    0°Initial, 0 cm Initial, 0 s Corotron Charger  87.3° 2.29 0.18 LaserStrike 147.7° 3.87 0.305 Probe #1 173.2° 4.53 0.36 Probe #2 245.9° 6.440.51 Erase Bar Center   360° 9.425 0.74The erase bar is an array of laser emitting diodes (LED) with awavelength of 720 nm. that discharges the surface of theorganophotoreceptor. The corotron charger comprises a wire that permitsthe transfer of a charge to the surface of the organophotoreceptor atfast processing speeds.

From the table, the first electrostatic probe (Trek™ 344 electrostaticmeter) is located 0.055 s after the laser strike station and 0.18 safter the corotron charger. In addition, the second probe (Trek 344electrostatic meter) is located 0.15 s from the first probe and 0.33 sfrom the corotron charger. All measurements were performed at 20° C. and30% relative humidity.

Electrostatic measurements were obtained as a compilation of severaltests. The first three diagnostic tests (prodtest initial, VlogEinitial, dark decay initial) are designed to evaluate the electrostaticcycling of a new, fresh sample and the last three, identical diagnostictest (prodtest final, VlogE final, dark decay final) are run aftercycling of the sample (longrun). The laser is operated at 780 nm, 600dpi, 50 um spot size, 60 nanoseconds/pixel expose time, 1,800 lines persecond scan speed, and a 100% duty cycle. The duty cycle is the percentexposure of the pixel clock period, i.e., the laser is on for the full60 nanoseconds per pixel at a 100% duty cycle.

Electrostatic Test Suite:

1) PRODTEST: Charge acceptance (V_(acc)) and discharge voltage (V_(dis))were established by subjecting the samples to corona charging (erase baralways on) for three complete drum revolutions (laser off); dischargedwith the laser @ 780 nm & 600 dpi on the forth revolution (50 um spotsize, expose 60 nanoseconds/pixel, run at a scan speed of 1,800 linesper second, and use a 100% duty cycle); completely charged for the nextthree revolutions (laser off); discharged with only the erase lamp @ 720nm on the eighth revolution (corona and laser off) to obtain residualvoltage (V_(res)); and, finally, completely charged for the last threerevolutions (laser off). The contrast voltage (V_(con)) is thedifference between V_(acc) and V_(dis) and the functional dark decay(V_(dd)) is the difference in charge acceptance potential measured byprobes #1 and #2.

2) VLOGE: This test measures the photoinduced discharge of thephotoconductor to various laser intensity levels by monitoring thedischarge voltage of the sample as a function of the laser power(exposure duration of 50 ns) with fixed exposure times and constantinitial potentials. This test measures the photoinduced discharge of thephotoconductor to various laser intensity levels by monitoring thedischarge voltage of the sample as a function of the laser power(exposure duration of 50 ns) with fixed exposure times and constantinitial potentials. The functional photosensitivity, S_(780 nm), andoperational power settings can be determined from this diagnostic test.

3) DARK DECAY: This test measures the loss of charge acceptance in thedark with time without laser or erase illumination for 90 seconds andcan be used as an indicator of i) the injection of residual holes fromthe charge generation layer to the charge transport layer, ii) thethermal liberation of trapped charges, and iii) the injection of chargefrom the surface or aluminum ground plane.

4) LONGRUN: The sample was electrostatically cycled for 4000 drumrevolutions according to the following sequence per each sample-drumrevolution. The sample was charged by the corona, the laser was cycledon and off (80-100° sections) to discharge a portion of the sample and,finally, the erase lamp discharged the whole sample in preparation forthe next cycle. The laser was cycled so that the first section of thesample was never exposed, the second section was always exposed, thethird section was never exposed, and the final section was alwaysexposed. This pattern was repeated for a total of 4000 drum revolutions,and the data was recorded periodically, after every 200th cycle.

5) After the LONGRUN test, the PRODTEST, VLOGE, DARK DECAY diagnostictests were run again to obtain the final values.

The following Table shows the results from the prodtest initial andprodtest final diagnostic tests. The values for the charge acceptancevoltage (Vacc, probe #1 average voltage obtained from the third cycle),discharge voltage (Vdis, probe #1 average voltage obtained from thefourth cycle), and residual voltage (Vres, probe #1 average voltageobtained from the eighth cycle) are reported for the initial and finalcycles. TABLE 1 Dry Electrostatic Test Results: Initial and After 4000cycles. Prodtest Initial Prodtest Final Sample V_(acc) V_(dis) V_(con)S_(780 nm) V_(res) V_(acc) V_(dis) V_(con) V_(res) Sample 1 887 76 811222 26 595 69 526 33 Sample 2 984 85 899 236 27 653 68 585 27 Sample 3969 75 894 343 27 716 63 653 24 Sample 4 1231 68 1193 314 27 885 63 82228 Sample 5 915 78 837 210 29 622 73 549 34 Sample 6 977 84 893 222 27679 74 605 32 Sample 7 770 56 714 222 23 619 61 558 24 Sample 8 1067 89978 222 34 784 79 705 38 Comparative Sample A 905 61 844 210 21 618 58560 22 Comparative Sample B 967 54 913 236 21 652 55 597 30 Comparativesample C 1266 62 1204 290 25 864 63 801 34

Note: The data were obtained on a fresh sample at the beginning ofcycling and then after 4000 cycles. In the above table, the radiationsensitivity (Sensitivity at 780 nm in m²/J) of the xerographic processwas determined from the information obtained during the VLOGE diagnosticrun by calculating the reciprocal of the product of the laser powerrequired to discharge the photoreceptor to ½ of its initial potential,the exposure duration, and 1/spot size.

As understood by those skilled in the art, additional substitution,variation among substituents, and alternative methods of synthesis anduse may be practiced within the scope and intent of the presentdisclosure of the invention. The embodiments above are intended to beillustrative and not limiting. Additional embodiments are within theclaims. Although the present invention has been described with referenceto particular embodiments, workers skilled in the art will recognizethat changes may be made in form and detail without departing from thespirit and scope of the invention.

1. An organophotoreceptor comprising an electrically conductivesubstrate and a photoconductive element on the electrically conductivesubstrate, the photoconductive element comprising: (a) a chargetransport material having the formula

where n is an integer between 2 and 6, inclusive; R₁ and R₂ are,independently, H, halogen, carboxyl, hydroxyl, thiol, cyano, nitro,aldehyde group, ketone group, an ether group, an ester group, a carbonylgroup, an alkyl group, an alkaryl group, or an aryl group; X is alinking group having the formula —(CH₂)_(m)—, branched or linear, wherem is an integer between 0 and 20, inclusive, and one or more of themethylene groups can be optionally replaced by O, S, C═O, O═S═O, aheterocyclic group, an aromatic group, urethane, urea, an ester group, aNR₃ group, a CHR₄ group, or a CR₅R₆ group where R₃, R₄, R₅, and R₆ are,independently, H, an alkyl group, an alkaryl group, a heterocyclicgroup, or an aryl group; Y comprises a bond, C, N, O, S, a branched orlinear —(CH₂)_(p)— group where p is an integer between 0 and 10, anaromatic group, a cycloalkyl group, a heterocyclic group, or a NR₉ groupwhere R₉ is hydrogen atom, an alkyl group, or aryl group, wherein Y hasa structure selected to form n bonds with the corresponding X groups;and Z is a fluorenylidene group; and (b) a charge generating compound.2. An organophotoreceptor according to claim 1 wherein Y is an aromaticgroup and X is —S—C(═O)—.
 3. An organophotoreceptor according to claim 1wherein Y is a bond, O, S, or CH₂ and X is —(CH₂)_(m)— group where m isan integer between 0 and 20 and where at least one of the CH₂ groups isreplaced by O, S, C═O, O═S═O, an ester group, a heterocyclic group, oran aromatic group.
 4. An organophotoreceptor according to claim 1wherein the charge transport material has a formula selected form thegroup consisting of the following:


5. An organophotoreceptor according to claim 1 wherein thephotoconductive element further comprises a second charge transportmaterial.
 6. An organophotoreceptor according to claim 5 wherein thesecond charge transport material comprises a charge transport compound.7. An organophotoreceptor according to claim 1 wherein thephotoconductive element further comprises a binder.
 8. Anelectrophotographic imaging apparatus comprising: (a) a light imagingcomponent; and (b) an organophotoreceptor oriented to receive light fromthe light imaging component, the organophotoreceptor comprising anelectrically conductive substrate and a photoconductive element on theelectrically conductive substrate, the photoconductive elementcomprising (i) a charge transport material having the formula

where n is an integer between 2 and 6, inclusive; R₁ and R₂ are,independently, H, halogen, carboxyl, hydroxyl, thiol, cyano, nitro,aldehyde group, ketone group, an ether group, an ester group, a carbonylgroup, an alkyl group, an alkaryl group, or an aryl group; X is alinking group having the formula —(CH₂)_(m)—, branched or linear, wherem is an integer between 0 and 20, inclusive, and one or more of themethylene groups can be optionally replaced by O, S, C═O, O═S═O, aheterocyclic group, an aromatic group, urethane, urea, an ester group, aNR₃ group, a CHR₄ group, or a CR₅R₆ group where R₃, R₄, R₅, and R₆ are,independently, H, an alkyl group, an alkaryl group, a heterocyclicgroup, or an aryl group; Y comprises a bond, C, N, O, S, a branched orlinear —(CH₂)_(p)— group where p is an integer between 0 and 10, anaromatic group, a cycloalkyl group, a heterocyclic group, or a NR₉ groupwhere R₉ is hydrogen atom, an alkyl group, or aryl group, wherein Y hasa structure selected to form n bonds with the corresponding X groups;and Z is a fluorenylidene group; and (ii) a charge generating compound.9. An electrophotographic imaging apparatus according to claim 8 whereinY is an aromatic group and X is —S—C(═O)—.
 10. An electrophotographicimaging apparatus according to claim 8 wherein Y is a bond, O, S, or CH₂and X is —(CH₂)_(m)— group where m is an integer between 0 and 20 andwhere at least one of the CH₂ groups is replaced by O, S, C═O, O═S═O, anester group, a heterocyclic group, or an aromatic group.
 11. Anelectrophotographic imaging apparatus according to claim 8, wherein thecharge transport material has a formula selected form the groupconsisting of the following:


12. An electrophotographic imaging apparatus according to claim 8wherein the photoconductive element further comprises a second chargetransport material.
 13. An electrophotographic imaging apparatusaccording to claim 12 wherein second charge transport material comprisesa charge transport compound.
 14. An electrophotographic imagingapparatus according to claim 8 further comprising a liquid tonerdispenser.
 15. An electrophotographic imaging process comprising; (a)applying an electrical charge to a surface of an organophotoreceptorcomprising an electrically conductive substrate and a photoconductiveelement on the electrically conductive substrate, the photoconductiveelement comprising (i) a charge transport material having the formula

where n is an integer between 2 and 6, inclusive; R₁ and R₂ are,independently, H, halogen, carboxyl, hydroxyl, thiol, cyano, nitro,aldehyde group, ketone group, an ether group, an ester group, a carbonylgroup, an alkyl group, an alkaryl group, or an aryl group; X is alinking group having the formula —(CH₂)_(m)—, branched or linear, wherem is an integer between 0 and 20, inclusive, and one or more of themethylene groups can be optionally replaced by O, S, C═O, O═S═O, aheterocyclic group, an aromatic group, urethane, urea, an ester group, aNR₃ group, a CHR₄ group, or a CR₅R₆ group where R₃, R₄, R₅, and R₆ are,independently, H, an alkyl group, an alkaryl group, a heterocyclicgroup, or an aryl group; Y comprises a bond, C, N, O, S, a branched orlinear —(CH₂)_(p)— group where p is an integer between 0 and 10, anaromatic group, a cycloalkyl group, a heterocyclic group, or a NR₉ groupwhere R₉ is hydrogen atom, an alkyl group, or aryl group, wherein Y hasa structure selected to form n bonds with the corresponding X groups;and Z is a fluorenylidene group; and (ii) a charge generating compound.(b) imagewise exposing the surface of the organophotoreceptor toradiation to dissipate charge in selected areas and thereby form apattern of charged and uncharged areas on the surface; (c) contactingthe surface with a toner to create a toned image; and (d) transferringthe toned image to substrate.
 16. An electrophotographic imaging processaccording to claim 15 wherein Y is an aromatic group and X is —S—C(═O)—.17. An electrophotographic imaging process according to claim 15 whereinY is a bond, O, S, or CH₂ and X is —(CH₂)_(m)— group where m is aninteger between 0 and 20 and where at least one of the CH₂ groups isreplaced by O, S, C═O, O═S═O, an ester group, a heterocyclic group, oran aromatic group.
 18. An electrophotographic imaging process accordingto claim 15 wherein the charge transport material has a formula selectedfrom the group consisting of the following:


19. An electrophotographic imaging process according to claim 15 whereinthe photoconductive element further comprises a second charge transportmaterial.
 20. An electrophotographic imaging process according to claim19 wherein the second charge transport material comprises a chargetransport compound.
 21. An electrophotographic imaging process accordingto claim 15 wherein the photoconductive element further comprises abinder.
 22. An electrophotographic imaging process according to claim 15wherein the toner comprises a liquid toner comprising a dispersion ofcolorant particles in an organic liquid.
 23. a charge transport materialhaving the formula

where n is an integer between 2 and 6, inclusive; R₁ and R₂ are,independently, H, halogen, carboxyl, hydroxyl, thiol, cyano, nitro,aldehyde group, ketone group, an ether group, an ester group, a carbonylgroup, an alkyl group, an alkaryl group, or an aryl group; X is alinking group having the formula —(CH₂)_(m)—, branched or linear, wherem is an integer between 0 and 20, inclusive, and one or more of themethylene groups can be optionally replaced by O, S, C═O, O═S═O, aheterocyclic group, an aromatic group, urethane, urea, an ester group, aNR₃ group, a CHR₄ group, or a CR₅R₆ group where R₃, R₄, R₅, and R₆ are,independently, H, an alkyl group, an alkaryl group, a heterocyclicgroup, or an aryl group; Y comprises a bond, C, N, O, S, a branched orlinear —(CH₂)_(p)— group where p is an integer between 0 and 10, anaromatic group, a cycloalkyl group, a heterocyclic group, or a NR₉ groupwhere R₉ is hydrogen atom, an alkyl group, or aryl group, wherein Y hasa structure selected to form n bonds with the corresponding X groups;and Z is a fluorenylidene group.
 24. A charge transport materialaccording to claim 23 wherein Y is an aromatic group and X is —S—C(═O)—.25. A charge transport material according to claim 23 wherein Y is abond, O, S, or CH₂ and X is —(CH₂)_(m)— group where m is an integerbetween 0 and 20 and where at least one of the CH₂ groups is replaced byO, S, C═O, O═s═O, an ester group, a heterocyclic group, or an aromaticgroup.
 26. A charge transport material according to claim 23 wherein thecharge transport material has a formula selected from the groupconsisting of the following: